Katz is/was professor of Jewish Educational and Social History, Emeritus, at the Hebrew University of Jerusalem

Below is the end of the chapter, on the emergence of anti-Semitism, in Germany, around 1870.
Scholars distinguish between anti Judaism, before Jews in most West European countries were granted equal rights, around 1800, and anti-Semitism, what began around 1870.

Page 258, chapter ‘The incubation’.
‘The decisive factor in the anti-Semitic eruption was the failure to fulfil the condition upon which the eradication of Gentile suspicions of Jews had been predicated, namely, the disappearance of the tightly knit Jewish community. Far from disappearing, this community only assumed a new metamorphosis, not all aspects of which were regarded favourably by the Gentiles. Though Jews now were active inside German society, in economic life, culture, and politics, they nevertheless remained conspicuous as a group. Their pursuits, never centrally planned or directed, were determined by historical and sociological factors…….
And despite their integration, they stood out as a closely knit group’.

Page 259
‘What remained unimpaired was Jewish inbreeding, the maintaining of exclusively Jewish family ties. This, and the residues of that religious nonconformity, comparative economic co-operation, and social isolation, and some cultural peculiarity gave the Jewish group a special physiognomy. If the group was different from what it had been a century before, it certainly had not assumed the characteristics expected by those who propounded the idea of fusion with Christian society.

Thus, instead of completely disappearing as expected, the Jewish community merely underwent a transformation. And the old stereotypes were now revived. The wait-and-see attitude of the Gentile population, which involved the concealment and suppression of anti-Jewish sentiment, turned into overt resentment. This was the point at which anti-Semitism boiled over’.